alt Hacker News> The relevant use case is you come here to see links people share and comment on them. That's sufficiently "social" in this context.
Just having users submit links that other users can comment on doesn't make it social media. I can't follow particular users or topics, I can't leave myself a note about some user that I've had a positive or negative experience with, I can't ignore someone who I don't want to read, etc. Heck, usernames are so de-emphasized on this site that I almost always forget that they're there.
A rose by any other name. If you'd prefer I'd have said
"But for keeping up to date on news, people use link aggregation boards where other users post links to stuff on the web and then talk to each other about them. RSS isn't the missing piece of the puzzle for changing that, an app on top of RSS is. And in the absence of Reader, nothing has shown up to fill that role that can compete with just trading gossip on Hacker News."
... that would be the same point. RSS, by itself, is a protocol for finding out some site created new content and is just not particularly compelling by itself for the average user when they can use "link aggregation boards where other users post links to stuff on the web and then talk to each othe about them" instead.